Pull-tab connection



May 28, 1968 v L DUNN `3,385,471

PULL-,TAB CONNECTION Original Filed Nov. 25, 1964 A 2 Sheets-Sheet 1 s 5^ 43 N fm1 Ill 2 LLOYD G. DUNN ATTORNEY May28,1968 i LG. DUNN 3,385,471v

PULL-TAB CONNECTION INVENTOR.

LLOYD G. DUNN ATTORNEY United States Patent O 3,385,471 PULL-TAB CONNECTIN Lloyd G. Dunn, Lower Burrell, Pa., assigner to Aluminum Company of America, Pittsburgh, Pa., a corporation of Pennsylvania Original application Nov. 25, 1964, Ser. No. 413,875, now Patent No. 3,357,388, dated Dec. 12, 1967. Divided and this application May 26, 1967, Ser. No. 641,680

2 Claims. (Cl. 22S-54) ABSTRACT F THE DISCLSURE A method of securing a container opening tab to a container member by forming a convergent boss in the metal container member, placing an imperforate portion of a metal opening tab over the boss, supporting the interior of the boss, and pressing the tab and boss together to reduce the boss axially and induce outward ow of the metal of both thereby reversely folding the peripheral portions of both metal sheets to form a double hollow headed rivet.

This is a divisional application of my copending application, Ser. No. 413,875, tiled Nov. 25, 1964, now U.S. Patent No. 3,357,388. This invention relates to containers provided with attached opening tabs. More particularly the invention relates to attaching opening tabs to a container member such as a body, end or closure wall provided with a tear-out section so that the container may be opened by exerting opening force to the attached tab without the use of a special opening tool.

In incorporating an attached tab opening feature in a container, it is important to be able to securely attach the opening tab to a container member in a manner suited to high speed mass production methods. It is also important for many tab opening container applications that the container member to which the opening tab is attached bey imperforate so that the contents of the container are not subject to deterioration by contact with the atmosphere.

Attached tab easy opening means for containers have been found particularly useful on metal cans. In such application the opening tab is often attached to the metal can end, which is then joined to the can body in a conventional manner, as by double seaming. rThis invention is quite useful in such application, or in any application in which a metal tab is attached to a metal body, end or closure member of a container made entirely of metal or in part of such materials as cellulose ber, foil and cellulose fiber laminate, glass, or plastic.

The tab opening container member ordinarily has a section, deiined by a score line or score lines, which is to be removed by exerting force on the tab to allow access to the container contents. In some instances this tear-out section is a relatively small panel defined by one continuous score line. This type of tear-out section or panel is normally employed on containers used for liquids such as beverages, oils, etc. On the other hand, in the case of containers for solids or semi-solids, a larger opening is usually desired to facilitate easy access to the contents, and a panel to be removed may be defined either by one continuous score line or by a peripheral tear strip formed by two substantially parallel score lines. In either case, the opening tab is attached to the tear-out section, and must be secured in such a manner that the joint between the tab and the tear-out section will not fail when force is exerted on the tab to initially rupture the score line or lines and to continue such rupture therealong during the opening process.

Heretofore opening tabs have been attached to con- 3,385,47l Patented May 23, 1968 Cice tainer members by hollow rivets made from the metal of the container members, such rivets being formed Iby a series of forming steps to achieve relatively straight sided hollow rivets of sutlicient height to extend through a tab aperture and then be headed over the tab. A single draw operation to form such a hollow rivet will usually fracture the metal, either during the draw or the subsequent heading operation. Fractured container members are unsatisfactory as the containers are then not sufficiently airtight to prevent deterioration of the packaged contents. Even with a series of draws to form a rivet of sufcient height, the rivet metal will often fracture upon heading because the total surface area of the finished rivet is much greater than the area of the container member from which the rivet is formed, the metal oi the rivet being greatly stretched and thinned. Also, headed rivets formed from the stretched and thinned metal often are not strong enough to withstand the force necessarily encountered in opening the container.

It is an object of this invention to provide an improved attachment of an opening tab to a container member.

A further object of this invention is to provide an improved method of securely attaching an opening tab to a tear-out section of a container so that the container may be opened without the use of a special opening tool.

Another object of the invention is to provide an improved method of mechanically attaching an opening tab to a container member wherein the tab and container member are provided with interlocking portions providing the desired mechanical connection without fracture of the container member.

Another object of this invention is to provide an improved method of securely attaching an opening tab to a container member that can be readily adapted to high speed mass production.

In accordance with this invention a hollow boss is provided in a container member to which anopening tab is to be attached. Both the container member and the tab are made of sheet metal, preferably aluminum, but other ductile metals may be used. Surprisingly, thin gage metal used in commercial can ends works quite well, even at a hard roll temper. The boss is a convergent boss in the sense that it is so formed that it has a distinctly convergent shape throughout the major part of its departure from the plane of the parent material from which it is formed. The particular shape of the convergent boss may vary within the description just provided, but for most applications I have found a generally dome-'shaped boss, which may approximate a spherical segment, to be satisfactory. The convergent boss may be formed in a single draw operation, which is a signilicant advantage in the mass production of container members. As mentioned above, a hollow upstanding rivet heretofore was usually formed by a series of forming steps to achieve a relatively straight sided hollow rivet of suicient height to pass through an aperture in the tab. Although a draw operation forming the boss employed in accordance with the present invention thins that portion of the metal forming the boss, the draw operation does not appreciably weaken the metal to the point of causing a fracture during the subsequent forming operation. One important feature of this invention is that a tab can be attached to a container member by means of a double metal layer integral rivet formed directly from the boss me-tal and the tab metal without fracturing either, and yet provide sutlicient strength to withstand the force applied to open the container.

Another operation desirably performed is that of scoring the container member so that the boss of the container member lies within a tear-out section dened by such scoring. Scoring may be done in a step separate from the boss forming operation or it may be done at the same time the boss is formed.

To attach the opening tab to the container member, the opening tab is positioned over the convergent boss, so that an imperforate portion of the tab completely overlies the boss, and the two are joined as hereinafter described. It is desirable that a similar convergent boss also be provided in the portion of the tab overlying the container member boss, although it is not necessary that a boss be formed in the tab. When a convergent boss in the tab is used it may be of substantially fthe same size and shape as that formed in the container member, but it need not be of identical dimensions. In the previously known riveting method referred to above the tab has an aperture and the hollow upstanding rivet protrudes through this aperture prior to forming the head. The operation of assembling such a tab over the rivet, so that the tab is seated properly, particularly in mass production, requires rather close control. Faulty seating of Athe tab will usually produce a Weak tab attachment and often fail when opening force is applied. The preferred method of using a tab with a boss similar to that in the container member, has the advantage of permitting registration of the tab more easily and accurately in contiguous overlying relationship with the boss of the container member, due to the tendency of the boss of the tab to seat itself over `the boss of the container in proper position and alignment.

When the opening tab is provided with a convergent boss, it may be formed in a single draw operation in the manner described above for the convergent boss formed in the container member. In some cases it will be convenient for both the boss of the tab and the boss of the container member to be formed simultaneously, as by placing the opening tab over the container member and performing the single forming operation on the two layers of metal at once. In this case the boss of the container member will be intimately nested in the overlying tab boss, and will be slightly smaller than the tab boss.

The operation of attaching the opening tab to the container member is that of reforming by a single pressure step or operation the convergent boss of the container member and the overlying portion of the tab to interlock the same in a headed condition with the container member boss being converted into a hidden rivet and the exposed rivet being that formed in the tab. This is accom-i plished by inserting a back-up anvil into the interior of the container member boss, which anvil is spaced from the closed end of the boss, and applying pressure to the boss of the container member and the overlying portion of the tab either by an impact blow or squeezing to produce suicient permanent deformation of the metal for a headed double rivet joint. The back-up anvil is maintained rigid during the reforming and heading operation and supports the interior of the container member boss against lateral inward collapse of the metal during such operation. The pressure is desirably applied to the boss of the container member and the overlying portion of the tab, to induce outward or radial flow of the metal in both, i.e. to cause the same to move in directions normal to the direction of the applied pressure and to reduce axially the height of the boss (or bosses, as the case may be), thereby forming interlocking peripheral beads for secure jointure of the tab to the container member. The back-up anvil is spaced from the closed end of the container mem- -ber boss so that the desired metal ow during reforming of the convergent boss or bosses into the resultant headed rivet may be achieved. The jointure is accomplished when the outer or peripheral walls of the container member boss and overlying portion of the tab are caused to fold back (that is reversely of the direction of radial flow) in an interlocked condition once the overlying portions of each are outwardly extended by the applied pressure beyond the peripheral edge of the back-up anvil. By this method there is produced a strong interlocking joint between the container member and the opening tab. The radial flow in `this operation produces transverse end portions of the headed double rivet that are of thinned crosssection, but these portions ofthe headed rivet are not subjected to the same amount of stress during opening of the container as are the reversely folded wall portions forming the interlocking peripheral beads. The latter are not thinned as much as the transverse end portions of the headed double rivet by the reforming and heading operation, so they are sufliciently strong where strength is most needed. This method of integral hollow rivet attachment of tab to container provides a double metal thickness in the critical stress areas of the peripheral beads formed by the reversely folded wall portions, with both the tab metal and the container member metal contributing strength to these areas.

The invention may be further understood from the following detailed description, referring to the accompanying drawings, in which.

FIG. 1 is a fragmentary perspective view of a top of a can utilizing the invention;

FIG. 2 is a plan view of the same can top;

FIG. 3 is an enlarged sectional view of a mandrel and die, showing a container member in position just prior to boss forming;

FIG. 4 is an enlarged sectional view showing the same container member after boss forming, with the mandrel and die in the closed position;

FIG. 5 is an enlarged sectional view similar to FIG. 3, but showing a mandrel, die and container member in position prior to boss forming and scoring in the same operation;

FIG. 6 is an enlarged sectional view showing the same mandrel and die in a partially closed position during boss forming and scoring in the same operation;

FIG. 7 is an enlarged sectional view showing the same mandrel and die in closed position after boss forming and scoring of the container member;

FIG. 8 is a plan view of a can end after boss forming and scoring, showing the boss located at the terminal end of the tear-strip;

FIG. 9 is an enlarged sectional view showing an opening tab boss positioned on a container member boss, between a punch and anvil for a heading operation;

FIG. 10 is an enlarged sectional view showing a tab positioned on a container member, with bosses in each that were formed simultaneously, the view also showing a punch and anvil for the heading operation;

FIG. 11 is a view similar t0 FIGS. 9 and 10, showing the punch and anvil for the heading operation partially closed;

FIG. 12 is another similar view, showing the punch and anvil for the heading Voperation closed, with the tab and container member joined by the heading oper-ation;

FIG. 13 is an enlarged sectional view showing a tab without a boss positioned on the container member boss, between a punch and anvil for the heading operation;

FIG. 14 is a view similar to FIG. 13, showing the punch and an anvil partially closed, with the tab and container member joined; and

FIG. 15 is another similar view, showing the punch and anvil closed, with the tab and container member joined; and

FIG. 16 is a larger sectional view of a finished integral rivet joint between a container member and an opening tab taken along line A--A in FIG. 2.

Referring to FIG. l, the invention may be employed in connection with a metal can body 1 provided with a metal container member 2, such as a can end. The member 2 may be provided with score lines 3 defining a tearstrip 4 to remove the tear-out panel. Other types of container bodies may be utilized, such as glass, foil and fiber laminate, or plastic. The container member 2 is scored or weakened along the lines 3 to form a tear-strip 4 that extends around the container member near the periphery. Thus, severance and removal of the tear-strip removes a substantial portion of the container member, allowing laccess to the packaged contents. The scoring can vary from that shownin FIG. 1 and is not restricted to any particular tear-strip conguration, nor to a tear-strip configuration as a single continuous-score line may be used to dene a panel tear-out section. As shown in FIG. 2, an opening ltab 6 is attached to the tear strip 4, in close proximity to the terminalend 5, byy means of a double metal layer integral rivet 7. The opening tab 6 provides the gripping means for force to be manually exerted on the tear-strip to initially rupture the container member 2 at the tear-strip terminal end 5 and to continue severance along the score linesv 3, for removal .of thetearstrip 4 and the tear-out section ofthe containerl member. The opening tab may be either the outwardly bendable type or the rigid lever type. In utilizing a container opening means regardless of type or kind of opening tab, it is very important that the opening tab be securely attached to the container member so that, when opening force is exerted on the tab, the joint between the'tab, andl cntainer member does not fail. j l

FIG. 3 shows the mandrel and die arrangement just prior to the forming of a boss in a container member. The same mandrel and die arrangement may be ernployed for forming a boss in a tab. As shown, a container member 2 is placed between the upper die 8 and the nose 11 of cooperating mandrel 9. The die 8 has a cylindrical recess 10 of the diameter desired for the boss. The mandrel 9 is supported and maintained in proper position by a mandrel holder 22, and has a dome-shaped nose 11 of the size and shape desired for the boss. FIG. 4 shows the completed boss forming operation, with the die 8 and mandrel 9 in closed position, wherein a portion of the container member 2 is drawn without rupture into a hollow, dome-shaped boss. It is to be noted that this single boss forming operation will only slightly thin and stretch the metal making up the boss, so that for subsequent operations the metal has not been detrimentally affected.

Scoring of the container member may be done either in a separate operation, by conventional scoring means, or by scoring at the same time as the convergent boss is formed in the container member. The depth of the score will depend upon the metal used and the type of product to be packaged in the container. Scoring and boss forming simultaneously is shown in FIGS. 5, 6 and 7, wherein the cooperating die and mandrel are arranged and operated as previously described, except that the die 8 carries a suitable scoring projection 12 that will provide the desired score configuration and depth. Combining the scoring and boss forming operation into one simultaneous operation is preferred as this eliminates a separate work handling operation. The container member 2 may have the conguration shown in FIG. 8 after the boss has been formed and the scoring completed. The convergent boss 13 is located in close proximity to the terminal end 5 of the tear-strip 4, and is within the score lines 3 which form a continuous score line.

The opening tab in the preferred embodiment of my invention has a convergent boss formed in an imperforate portion of it in the same manner, and of the same or substantially similar size and shape, as that formed in the container member. If desired the container member boss and tab boss can be drawn simultaneously simply by placing the opening tab over the container member and performing the single draw as described above.

The joining operation is shown sequentially in FIGS. 9 or l0, followed by FIGS. 11 and 12. In FIG. 9 the imperforate area of the opening tab 6 carrying a convergent boss 14 is superimposed over the container member boss 13, with the container member boss 13 extending into the tab boss 14. The container member 2 is positioned on a lower die 15 with an anvil portion 16, which is non-complementary with the container member boss, and has substantially vertical side Walls 16a and a liat top 16b extending into the interior of the container member boss 13 and spaced from the closed end of the boss. The anvil portion 16 is spaced from the closed end of the container .headed rivet. The anvil portion 16 should` be suticiently high to permit the metal of the container boss and of the tab boss to reversely fold and interlock to form the joint,

once the overlying portions of the bosses are outwardly extended by the applied pressure beyond the peripheral edge of the back-up anvil. Ordinarily the height of the anvil portion 16 will be at least the total original thickness of themetal of both the container member and the opening tab. 'I'he anvil portion 16 is maintained rigid during the reforming and heading operation and supports the interior of the container member boss against lateral inward collapse of the metal during such operation. The lower die assists in reversely folding the metal to form the interlocking peripheral beads by backing up the metal around the container member boss during the rivet forming operation, and the height of the anvil portion 16 is limited by that function of the lower die. A at punch 17 is provided.

FIG. l0 shows a similar arrangement, except that the position of the tab boss 14a in relation to the container member boss 13a is that obtained when both bosses have been drawn simultaneously as mentioned above.

As shown in FIGS. 11 and 12 the punch 17 in cooperation with the lower die 15 and anvil portion 16 applies the necessary pressure to the convergent bosses 13b and 14b, to induce outward or radial flow ofthe metal in both the container member boss and the tab boss, the metal flow occurring in directions normal to the direction in which the pressure is applied, and to reduce axially the height of the bosses. Either the punch 17 or lower die 15 or both may be moved to apply the pressure. The squeezed metal of the tab 14c and container member 13e is thereby thinned across the resultant transverse head of the double rivet formed at the same time as the peripheral wall portions are reversely folded to form the interlocked opening tab peripheral bead 18 and the container member peripheral bead 19 to make a double metal layer hollow headed rivet which joins the tab 6 to the container member 2. The vertical walls 16a of the anvil portion '16 support the reversely folded interlocked portions against inward collapse.

This heading operation is a one-step operation, and FIG. 11 merely shows an intermediate stage in the metal flow.

FIGS. 13 and 14 and 15 show sequentially the formation of the double integral rivet wherein the imperforate area of the opening tab 6 does not carry a preformed boss. The method, die arrangement and resultant double integral rivet are essentially the same as described above for an opening tab which does have a preformed hollow boss. The desired registration of the tab in overlying contiguous arrangement with the container member boss may be more difficult than when the tab does have a boss to help in its proper positioning and alignment with the container member boss, but a separate boss-forming operation may be avoided when a tab without a boss is used. FIG. 14 shows the metal ow in the portion 14b of the opening tab 6 and in the container member convergent boss 13b after partial completion of the heading operation of the rivet. In FIG. 15 the punch 17 and cooperating lower die y15 and anvil portion 16 are in the closed position and the headed rivet is fully formed, with the tab peripheral bead 18 in interlocking relationship with the container member peripheral bead 19, the metal being reversely folded in a downward direction as it is extended laterally beyond the back-up anvil 16.

FIG. 16 shows a cross section of a completed double metal layer integral hollow rivet joint made in accordance with this invention, taken along line A-A in FIG. 2. It should be noted that as a result of the heading operation the thinned metal 14C and 13e in the opening tab and in the container member, making up -the transverse head of the rivet, is thinned primarily across the transverse end portions of the rivet. The metal at the interlocking peripheral 7` beads 18 and 19 is only slightly thinned. This is desirable as the interlocking peripheral beads 18 and 19 consist of metal not signicantly thinned so that the metal thickness in the peripheral bead of each metal layer is substantially greater than the metal thickness in the transverse end portion of the same metal layer. t

The description in specific detail of the selected practice of the invention will suggestto those skilled in the art, various changes, substitutions and other departures from my disclosure within the spirit and scope of the appended claims.

What is claimed is: 1.. The combination of, a container member and attached opening tab, comprising:

a sheet metal container member, and a sheet metal opening tab having an imperforate area attached to the container member, by means of a headed double metal layer hollow rivet comprising transverse end portions and interlocking peripheral beads formed from container member metal and opening tab metal, the metal thickness in the peripheral bead of each metal layer being substantially greater than the metal thickness inthe transverse end portion of the same metal layer.

2. The combination of a container member and attached opening tab, comprising:

a sheet metal container member provided with a score line to define a tear-out section with a terminal end, and

a sheet metal opening tab having an imperforate area attached to said tear-out section in close proximity to the terminal end thereof, by means of a headed double metal layer hollow rivet comprising transverse end portions and interlocking peripheral beads formed from container member metal and opening tab metal, the metal thickness in the peripheral bead of each metal layer being substantially greater than the metal thickness in the transverse end portion of the same metal layer.

References Cited UNITED STATES PATENTS 3,198,155 8/1965 Fraze 113-121 THERON E. CONDON, Primary Examiner.

G. T. HALL, Assistant Examiner. 

